Ban kicked players from instance for the remainder of said instance.
When a person is kicked for harassment/afk/whatever other reason they have the opportunity to join again through duty finder's "Join in progress". Multiple times I have experienced a person being kicked and then sits with DF open queueing for the instance and manages to join multiple times.
Party members can only vote to kick once every 4 hours so after 3 rejoins the griefer can just sit there afk until everybody has to abandon.
Banning the player from entering that specific instance after being kicked will remove this common griefing tactic.
*EDIT*
A lot of people are misinterpreting this, so I'm going to write a quick scenario which explains the process.
A party starts a dungeon, at some point, one is kicked. This kicked player is banned from that particular instance, which means that if they requeue with "In-progress" they cannot enter that specific party's dungeon again, but will be offered a different one. They can also choose to queue for a fresh instance of that dungeon, if they so wish.
The ban only applies to that specific instance with that specific group of players.